This invention relates to an electrical lamp, and means for plugging the lamp into a low-voltage rail having a central longitudinal portion or track, and intermittent transverse portions supporting longitudinal side strips spaced apart from the track on opposite sides of it.
Extendable voltage rails, for use in supplying alternating current to electrical lamps at an appropriate voltage (e.g. 220 volts), are known to afford variable lighting arrangements for office spaces, display windows and the like. Lights of different design, but in particular halogen lamps, can be clamped along the voltage rail at random locations, depending upon lighting requirements. The clamping procedure provides both the mechanical support and the electrical contact. Because of possible danger from the high voltage, the voltage rail and light clamping socket must include safeguards against direct contact with current carrying structure.
These lights are relatively large and heavy, such that the mechanical support must be correspondingly strong. Consequently, clamping sockets or other clamping connectors are expensive, complex and therefore costly.
German Pat. No. (DE-GM 86 33 279) discloses a low-voltage rail for supporting miniature lamps when clamped onto the rail. The rail is plastic, and includes a longitudinally running central part or track, and two side rails parallel to the central track. Intermittent cross-pieces or lateral portions support the side rails at a selected distance from the central track. Free-lying, bare conductor wires are placed or clipped in and held on the cross-pieces, and run longitudinally along the two spaces between the central track and side rails. Miniature, low-voltage lamps can be plugged into the clamping socket with the two connecting wires projecting out from the miniature lamps capable of being plugged in through the socket. The socket base, with two connecting wires plugged through, has socket support surfaces that lie against the conductor wires of the rail, with interposition of the clamp connecting wires to form an electrical contact. Two socket support surfaces or fork-shaped walls face one another to grip the central track and provide the mechanical support.
These miniature lamps, however, are firmly seated with their sockets and are limited to adjustment on the low-voltage rail in the longitudinal direction. This unduly restricts the directions in which illumination is possible. Additionally, the miniature lamps and their sockets comprise very small parts of low mass that project only slightly past the low-voltage rail. Because of this, they afford relatively little support. Therefore, the support is not strong enough for larger and heavier plug-in lights, in particular for low-voltage halogen lamps having an integral reflector and an extension piece or neck. The increased forces and pitching moments are too demanding for the conventional structure to provide sufficient support.
An object of the present invention is to provide a lamp, in particular a lamp capable of being plugged onto a low-voltage rail and adjustable over a wide range of different beam directions. Another object is to provide a lamp shade suitable for accommodating a reflector and that can properly dissipate the heat coming from the reflector. The heat loading of the entire lamp must be as little as possible so that practically all lamp parts (up to the lamp and possibly the reflector, along with other nonessential protective parts) can be injection molded from plastic. The lamp must be mechanically simple in design, and able to be produced in cost-effective fashion with the aid of known plastic injection molding techniques. Finally, another object of the invention is to provide a lamp capable of being plugged onto conventional low-voltage rails. In particular, the lamp should have a clamping socket that forms the electrical connection as well as a good mechanical support, with the lamp capable of being clamped and displaced at numerous arbitrary locations along the low-voltage rail.